A large number of chemical and biological reactions are pH-influenced. That is, the pH of a reaction environment influences the rate, selectivity, etc., of the chemical and/or biological reaction. Current methods/systems for controlling the pH of a reaction environment include sequential addition of an acid and/or base and selective water hydrolysis (e.g., with use of a membrane). However, current methods/systems have many disadvantages, including the need to replenish reagents (e.g., acid and/or base), inaccurate and/or imprecise pH changes, and irreversibility. Accordingly, improved methods and/or systems are needed.